1. Field of the Invention.
The invention relates to a process for improving a glycerolysed oil; it also relates to the oils thus improved.
2. Description of the Prior Art.
As is known, glycerolysed oils, which are well known as excipients in the pharmaceutical industry, are obtained by glycerolysis in the presence of alkaline catalysts. In one embodiment, these oils contain a residual glycerol level at most equal to one percent (1%).
In the text and the claims, "glycerolysed oil" designates a natural oil of plant or animal origin which has undergone alcoholysis treatment with glycerol, or a direct esterification of its fatty acids on glycerol.
These glycerolysed oils are essentially characterized by the fact that they consist of a mixture of mainly mono- and diesters of glycerol and of a smaller quantity of triesters. These glycerolysed oils must contain at least 90% by weight of glycerides (FDA-21 CFR requirements--Chapter I--.sctn.184.1505), and must have a high proportion (at least 50% and in practice of the order of 80%) of unsaturated fatty acids. Oils which may be mentioned are those of plant origin, such as those of corn, sunflower (high and low linoleic acid content) safflower (high and low linoleic acid content), palm (fractionated or otherwise), groundnut or colza, or of animal origin, such as that of tallow.
However, these glycerolysed oils have the bad tendency, when they are stored at room temperature, to crystallize partially and gradually, forming small white crystals which settle after a few hours to several days depending on the thermal history of the samples. These white crystals swell rapidly and render this oil unsuitable for its use as pharmaceutical excipient and partially mask the properties of the active ingredients.
To prevent the formation of these crystals, it has been suggested to add to the oil during the glycerolysis unsaturated fatty acids which form esters which do not precipitate. Unfortunately, this solution is poorly adapted to the pharmaceutical industry since the oil thus treated does not always correspond to the requirements of international standards for the "glycerolysed oil" designation, especially to the requirements of the GRAS (generally recognized as safe) standard based on the FDA (Food and Drug Administration) rules mentioned above.